Dry-milled soybeans are extracted with supercritical carbon dioxide at pressures 270 to 375 atm, temperature 50 to 70℃, solvent flow rates 0.025 to 0.16 cm/sec as linear velocity in the bed at super-critical state, and three types of soybean particle size in the range 0.05 to 0.02828 cm.
Under these conditions, extraction rates of soybean oil from solid substrates in a fixed bed(1.1mm I.D. 200mm Height) have been determined.
The extraction rates were constant during the initial extraction period where the film resistance controls the rates, and then, the rates shifted to time-dependent diffusion controlling mass transfer mode. To correlate these features, mass transfer calculations were carried out for the constant rate period and the subsequent unsteady mass transfer rate period, respectively.